eslint-plugin-unicorn

Unicorn

More than 100 powerful ESLint rules

You might want to check out XO, which includes this plugin.

Install

npm install --save-dev eslint eslint-plugin-unicorn

Requires ESLint >=9.20.0, flat config, and ESM.

Usage

Use a preset config or configure each rule in eslint.config.js.

If you don't use the preset, ensure you use the same languageOptions config as below.

import eslintPluginUnicorn from 'eslint-plugin-unicorn';
import globals from 'globals';

export default [
    {
        languageOptions: {
            globals: globals.builtin,
        },
        plugins: {
            unicorn: eslintPluginUnicorn,
        },
        rules: {
            'unicorn/better-regex': 'error',
            'unicorn/…': 'error',
        },
    },
    // …
];

Rules

💼 Configurations enabled in.\ ✅ Set in the recommended configuration.\ ☑️ Set in the unopinionated configuration.\ 🔧 Automatically fixable by the --fix CLI option.\ 💡 Manually fixable by editor suggestions.

Name	Description	💼	🔧	💡
better-regex	Improve regexes by making them shorter, consistent, and safer.		🔧
catch-error-name	Enforce a specific parameter name in catch clauses.	✅	🔧
consistent-assert	Enforce consistent assertion style with `node:assert`.	✅	🔧
consistent-date-clone	Prefer passing `Date` directly to the constructor when cloning.	✅ ☑️	🔧
consistent-destructuring	Use destructured variables over properties.			💡
consistent-empty-array-spread	Prefer consistent types when spreading a ternary in an array literal.	✅	🔧
consistent-existence-index-check	Enforce consistent style for element existence checks with `indexOf()`, `lastIndexOf()`, `findIndex()`, and `findLastIndex()`.	✅ ☑️	🔧
consistent-function-scoping	Move function definitions to the highest possible scope.	✅
custom-error-definition	Enforce correct `Error` subclassing.		🔧
empty-brace-spaces	Enforce no spaces between braces.	✅	🔧
error-message	Enforce passing a `message` value when creating a built-in error.	✅ ☑️
escape-case	Require escape sequences to use uppercase or lowercase values.	✅ ☑️	🔧
expiring-todo-comments	Add expiration conditions to TODO comments.	✅ ☑️
explicit-length-check	Enforce explicitly comparing the `length` or `size` property of a value.	✅	🔧	💡
filename-case	Enforce a case style for filenames.	✅
import-style	Enforce specific import styles per module.	✅ ☑️
new-for-builtins	Enforce the use of `new` for all builtins, except `String`, `Number`, `Boolean`, `Symbol` and `BigInt`.	✅ ☑️	🔧	💡
no-abusive-eslint-disable	Enforce specifying rules to disable in `eslint-disable` comments.	✅ ☑️
no-accessor-recursion	Disallow recursive access to `this` within getters and setters.	✅ ☑️
no-anonymous-default-export	Disallow anonymous functions and classes as the default export.	✅ ☑️		💡
no-array-callback-reference	Prevent passing a function reference directly to iterator methods.	✅		💡
no-array-for-each	Prefer `for…of` over the `forEach` method.	✅ ☑️	🔧	💡
no-array-method-this-argument	Disallow using the `this` argument in array methods.	✅ ☑️	🔧	💡
no-array-reduce	Disallow `Array#reduce()` and `Array#reduceRight()`.	✅
no-array-reverse	Prefer `Array#toReversed()` over `Array#reverse()`.	✅ ☑️		💡
no-array-sort	Prefer `Array#toSorted()` over `Array#sort()`.	✅ ☑️		💡
no-await-expression-member	Disallow member access from await expression.	✅	🔧
no-await-in-promise-methods	Disallow using `await` in `Promise` method parameters.	✅ ☑️		💡
no-console-spaces	Do not use leading/trailing space between `console.log` parameters.	✅ ☑️	🔧
no-document-cookie	Do not use `document.cookie` directly.	✅ ☑️
no-empty-file	Disallow empty files.	✅ ☑️
no-for-loop	Do not use a `for` loop that can be replaced with a `for-of` loop.	✅	🔧	💡
no-hex-escape	Enforce the use of Unicode escapes instead of hexadecimal escapes.	✅ ☑️	🔧
no-immediate-mutation	Disallow immediate mutation after variable assignment.	✅	🔧	💡
no-instanceof-builtins	Disallow `instanceof` with built-in objects	✅ ☑️	🔧	💡
no-invalid-fetch-options	Disallow invalid options in `fetch()` and `new Request()`.	✅ ☑️
no-invalid-remove-event-listener	Prevent calling `EventTarget#removeEventListener()` with the result of an expression.	✅ ☑️
no-keyword-prefix	Disallow identifiers starting with `new` or `class`.
no-lonely-if	Disallow `if` statements as the only statement in `if` blocks without `else`.	✅ ☑️	🔧
no-magic-array-flat-depth	Disallow a magic number as the `depth` argument in `Array#flat(…).`	✅ ☑️
no-named-default	Disallow named usage of default import and export.	✅ ☑️	🔧
no-negated-condition	Disallow negated conditions.	✅ ☑️	🔧
no-negation-in-equality-check	Disallow negated expression in equality check.	✅ ☑️		💡
no-nested-ternary	Disallow nested ternary expressions.	✅	🔧
no-new-array	Disallow `new Array()`.	✅ ☑️	🔧	💡
no-new-buffer	Enforce the use of `Buffer.from()` and `Buffer.alloc()` instead of the deprecated `new Buffer()`.	✅ ☑️	🔧	💡
no-null	Disallow the use of the `null` literal.	✅	🔧	💡
no-object-as-default-parameter	Disallow the use of objects as default parameters.	✅ ☑️
no-process-exit	Disallow `process.exit()`.	✅ ☑️
no-single-promise-in-promise-methods	Disallow passing single-element arrays to `Promise` methods.	✅ ☑️	🔧	💡
no-static-only-class	Disallow classes that only have static members.	✅ ☑️	🔧
no-thenable	Disallow `then` property.	✅ ☑️
no-this-assignment	Disallow assigning `this` to a variable.	✅ ☑️
no-typeof-undefined	Disallow comparing `undefined` using `typeof`.	✅ ☑️	🔧	💡
no-unnecessary-array-flat-depth	Disallow using `1` as the `depth` argument of `Array#flat()`.	✅ ☑️	🔧
no-unnecessary-array-splice-count	Disallow using `.length` or `Infinity` as the `deleteCount` or `skipCount` argument of `Array#{splice,toSpliced}()`.	✅ ☑️	🔧
no-unnecessary-await	Disallow awaiting non-promise values.	✅ ☑️	🔧
no-unnecessary-polyfills	Enforce the use of built-in methods instead of unnecessary polyfills.	✅ ☑️
no-unnecessary-slice-end	Disallow using `.length` or `Infinity` as the `end` argument of `{Array,String,TypedArray}#slice()`.	✅ ☑️	🔧
no-unreadable-array-destructuring	Disallow unreadable array destructuring.	✅ ☑️	🔧
no-unreadable-iife	Disallow unreadable IIFEs.	✅ ☑️
no-unused-properties	Disallow unused object properties.
no-useless-collection-argument	Disallow useless values or fallbacks in `Set`, `Map`, `WeakSet`, or `WeakMap`.	✅ ☑️	🔧
no-useless-error-capture-stack-trace	Disallow unnecessary `Error.captureStackTrace(…)`.	✅ ☑️	🔧
no-useless-fallback-in-spread	Disallow useless fallback when spreading in object literals.	✅ ☑️	🔧
no-useless-length-check	Disallow useless array length check.	✅ ☑️	🔧
no-useless-promise-resolve-reject	Disallow returning/yielding `Promise.resolve/reject()` in async functions or promise callbacks	✅ ☑️	🔧
no-useless-spread	Disallow unnecessary spread.	✅ ☑️	🔧
no-useless-switch-case	Disallow useless case in switch statements.	✅ ☑️		💡
no-useless-undefined	Disallow useless `undefined`.	✅ ☑️	🔧
no-zero-fractions	Disallow number literals with zero fractions or dangling dots.	✅ ☑️	🔧
number-literal-case	Enforce proper case for numeric literals.	✅ ☑️	🔧
numeric-separators-style	Enforce the style of numeric separators by correctly grouping digits.	✅ ☑️	🔧
prefer-add-event-listener	Prefer `.addEventListener()` and `.removeEventListener()` over `on`-functions.	✅ ☑️	🔧
prefer-array-find	Prefer `.find(…)` and `.findLast(…)` over the first or last element from `.filter(…)`.	✅ ☑️	🔧	💡
prefer-array-flat	Prefer `Array#flat()` over legacy techniques to flatten arrays.	✅ ☑️	🔧
prefer-array-flat-map	Prefer `.flatMap(…)` over `.map(…).flat()`.	✅ ☑️	🔧
prefer-array-index-of	Prefer `Array#{indexOf,lastIndexOf}()` over `Array#{findIndex,findLastIndex}()` when looking for the index of an item.	✅ ☑️	🔧	💡
prefer-array-some	Prefer `.some(…)` over `.filter(…).length` check and `.{find,findLast,findIndex,findLastIndex}(…)`.	✅ ☑️	🔧	💡
prefer-at	Prefer `.at()` method for index access and `String#charAt()`.	✅ ☑️	🔧	💡
prefer-bigint-literals	Prefer `BigInt` literals over the constructor.	✅ ☑️	🔧	💡
prefer-blob-reading-methods	Prefer `Blob#arrayBuffer()` over `FileReader#readAsArrayBuffer(…)` and `Blob#text()` over `FileReader#readAsText(…)`.	✅ ☑️
prefer-class-fields	Prefer class field declarations over `this` assignments in constructors.	✅ ☑️	🔧	💡
prefer-classlist-toggle	Prefer using `Element#classList.toggle()` to toggle class names.	✅ ☑️	🔧	💡
prefer-code-point	Prefer `String#codePointAt(…)` over `String#charCodeAt(…)` and `String.fromCodePoint(…)` over `String.fromCharCode(…)`.	✅ ☑️		💡
prefer-date-now	Prefer `Date.now()` to get the number of milliseconds since the Unix Epoch.	✅ ☑️	🔧
prefer-default-parameters	Prefer default parameters over reassignment.	✅ ☑️		💡
prefer-dom-node-append	Prefer `Node#append()` over `Node#appendChild()`.	✅ ☑️	🔧
prefer-dom-node-dataset	Prefer using `.dataset` on DOM elements over calling attribute methods.	✅ ☑️	🔧
prefer-dom-node-remove	Prefer `childNode.remove()` over `parentNode.removeChild(childNode)`.	✅ ☑️	🔧	💡
prefer-dom-node-text-content	Prefer `.textContent` over `.innerText`.	✅ ☑️		💡
prefer-event-target	Prefer `EventTarget` over `EventEmitter`.	✅ ☑️
prefer-export-from	Prefer `export…from` when re-exporting.	✅	🔧	💡
prefer-global-this	Prefer `globalThis` over `window`, `self`, and `global`.	✅ ☑️	🔧
prefer-import-meta-properties	Prefer `import.meta.{dirname,filename}` over legacy techniques for getting file paths.		🔧
prefer-includes	Prefer `.includes()` over `.indexOf()`, `.lastIndexOf()`, and `Array#some()` when checking for existence or non-existence.	✅ ☑️	🔧	💡
prefer-json-parse-buffer	Prefer reading a JSON file as a buffer.		🔧
prefer-keyboard-event-key	Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`.	✅ ☑️	🔧
prefer-logical-operator-over-ternary	Prefer using a logical operator over a ternary.	✅ ☑️		💡
prefer-math-min-max	Prefer `Math.min()` and `Math.max()` over ternaries for simple comparisons.	✅ ☑️	🔧
prefer-math-trunc	Enforce the use of `Math.trunc` instead of bitwise operators.	✅ ☑️	🔧	💡
prefer-modern-dom-apis	Prefer `.before()` over `.insertBefore()`, `.replaceWith()` over `.replaceChild()`, prefer one of `.before()`, `.after()`, `.append()` or `.prepend()` over `insertAdjacentText()` and `insertAdjacentElement()`.	✅ ☑️	🔧
prefer-modern-math-apis	Prefer modern `Math` APIs over legacy patterns.	✅ ☑️	🔧
prefer-module	Prefer JavaScript modules (ESM) over CommonJS.	✅ ☑️	🔧	💡
prefer-native-coercion-functions	Prefer using `String`, `Number`, `BigInt`, `Boolean`, and `Symbol` directly.	✅ ☑️	🔧
prefer-negative-index	Prefer negative index over `.length - index` when possible.	✅ ☑️	🔧
prefer-node-protocol	Prefer using the `node:` protocol when importing Node.js builtin modules.	✅ ☑️	🔧
prefer-number-properties	Prefer `Number` static properties over global ones.	✅ ☑️	🔧	💡
prefer-object-from-entries	Prefer using `Object.fromEntries(…)` to transform a list of key-value pairs into an object.	✅ ☑️	🔧
prefer-optional-catch-binding	Prefer omitting the `catch` binding parameter.	✅ ☑️	🔧
prefer-prototype-methods	Prefer borrowing methods from the prototype instead of the instance.	✅ ☑️	🔧
prefer-query-selector	Prefer `.querySelector()` over `.getElementById()`, `.querySelectorAll()` over `.getElementsByClassName()` and `.getElementsByTagName()` and `.getElementsByName()`.	✅	🔧
prefer-reflect-apply	Prefer `Reflect.apply()` over `Function#apply()`.	✅ ☑️	🔧
prefer-regexp-test	Prefer `RegExp#test()` over `String#match()` and `RegExp#exec()`.	✅ ☑️	🔧	💡
prefer-response-static-json	Prefer `Response.json()` over `new Response(JSON.stringify())`.	✅ ☑️	🔧
prefer-set-has	Prefer `Set#has()` over `Array#includes()` when checking for existence or non-existence.	✅ ☑️	🔧	💡
prefer-set-size	Prefer using `Set#size` instead of `Array#length`.	✅ ☑️	🔧
prefer-single-call	Enforce combining multiple `Array#push()`, `Element#classList.{add,remove}()`, and `importScripts()` into one call.	✅ ☑️	🔧	💡
prefer-spread	Prefer the spread operator over `Array.from(…)`, `Array#concat(…)`, `Array#{slice,toSpliced}()` and `String#split('')`.	✅	🔧	💡
prefer-string-raw	Prefer using the `String.raw` tag to avoid escaping `\`.	✅ ☑️	🔧
prefer-string-replace-all	Prefer `String#replaceAll()` over regex searches with the global flag.	✅ ☑️	🔧
prefer-string-slice	Prefer `String#slice()` over `String#substr()` and `String#substring()`.	✅ ☑️	🔧
prefer-string-starts-ends-with	Prefer `String#startsWith()` & `String#endsWith()` over `RegExp#test()`.	✅ ☑️	🔧	💡
prefer-string-trim-start-end	Prefer `String#trimStart()` / `String#trimEnd()` over `String#trimLeft()` / `String#trimRight()`.	✅ ☑️	🔧
prefer-structured-clone	Prefer using `structuredClone` to create a deep clone.	✅ ☑️		💡
prefer-switch	Prefer `switch` over multiple `else-if`.	✅ ☑️	🔧
prefer-ternary	Prefer ternary expressions over simple `if-else` statements.	✅ ☑️	🔧
prefer-top-level-await	Prefer top-level await over top-level promises and async function calls.	✅ ☑️		💡
prefer-type-error	Enforce throwing `TypeError` in type checking conditions.	✅ ☑️	🔧
prevent-abbreviations	Prevent abbreviations.	✅	🔧
relative-url-style	Enforce consistent relative URL style.	✅ ☑️	🔧	💡
require-array-join-separator	Enforce using the separator argument with `Array#join()`.	✅ ☑️	🔧
require-module-attributes	Require non-empty module attributes for imports and exports	✅ ☑️	🔧
require-module-specifiers	Require non-empty specifier list in import and export statements.	✅ ☑️	🔧	💡
require-number-to-fixed-digits-argument	Enforce using the digits argument with `Number#toFixed()`.	✅ ☑️	🔧
require-post-message-target-origin	Enforce using the `targetOrigin` argument with `window.postMessage()`.			💡
string-content	Enforce better string content.		🔧	💡
switch-case-braces	Enforce consistent brace style for `case` clauses.	✅	🔧
template-indent	Fix whitespace-insensitive template indentation.	✅	🔧
text-encoding-identifier-case	Enforce consistent case for text encoding identifiers.	✅ ☑️	🔧	💡
throw-new-error	Require `new` when creating an error.	✅ ☑️	🔧

Deleted and deprecated rules

See the list.

Preset configs

See the ESLint docs for more information about extending config files.

Note: Preset configs will also enable the correct language options.

Recommended config

This plugin exports a recommended config that enforces good practices.

import eslintPluginUnicorn from 'eslint-plugin-unicorn';

export default [
        // …
        eslintPluginUnicorn.configs.recommended,
        {
            rules: {
                'unicorn/better-regex': 'warn',
            },
        },
];

All config

This plugin exports an all that makes use of all rules (except for deprecated ones).

import eslintPluginUnicorn from 'eslint-plugin-unicorn';

export default [
        // …
        eslintPluginUnicorn.configs.all,
        {
            rules: {
                'unicorn/better-regex': 'warn',
            },
        },
];

Package detail